In the semiconductor photomask and nano-imprint lithography, complete removal of resist and other films from the substrate is required in order to form a low defective, finer pattern. During the process, a synthetic quartz glass substrate having a pattern-transferring thin film is used after a resist film and an optional protective film are formed thereon. The resist film and protective film must be completely removed from the substrate so that no residues may be left on the substrate.
In the prior art, from a substrate having resist and protective films coated thereon, the films are removed by dissolution using a suitable solvent containing a reagent capable of dissolving film components. When the substrate is pulled out of the solvent, the solvent having organic matter dissolved therein is carried over on the substrate surface, leaving the risk of secondary contamination.
It is then contemplated to peel the film from the substrate surface rather than dissolving the film on the substrate in a solvent. The method of peeling a resist film using ozone water is proposed. For example, WO 2007/138747 describes a method of peeling a resist film from a mask blank by treatment with ozone water having a certain ozone concentration.
This method, however, takes a long time until the resist film is peeled from the substrate. Because of the problem of increased process time, the method is industrially unacceptable at the present. For treatment with ozone water having a high ozone concentration, an intensified ozone generator and associated equipment to be installed therefor increase the capital investment. This leads to the increased production cost which is reflected by the price of products, which is unwanted to both the supply and demand sides.